1. Field of the Invention
The present invention relates to vascular images, or more particularly, to a system and method of using the frequency spectrum of a radio frequency (RF) signal backscattered from vascular tissue to identify at least one border on a corresponding vascular image.
2. Description of Related Art
The present invention relates to medical imaging arts. It finds particular application to a system and method of identifying a border on a vascular image (e.g., intra-vascular ultrasound (IVUS) image, Virtual Histology™ (VH) image, etc.). It should be appreciated that while the present invention is described in terms of identifying a luminal and medial-adventitial border on an IVUS or VH image, the present invention is not so limited. Thus, for example, identifying any border (or boundary) on any vascular image is within the spirit and scope of the present invention.
Ultrasonic imaging of portions of a patient's body provides a useful tool in various areas of medical practice for determining the best type and course of treatment. Imaging of the coronary vessels of a patient by ultrasonic techniques can provide physicians with valuable information. For example, the image data may show the extent of a stenosis in a patient, reveal progression of disease, help determine whether procedures such as angioplasty or atherectomy are indicated or whether more invasive procedures may be warranted.
In a typical ultrasound imaging system, an ultrasonic transducer is attached to the end of a catheter that is carefully maneuvered through a patient's body to a point of interest such as within a blood vessel. The transducer may be a single-element crystal or probe that is mechanically scanned or rotated back and forth to cover a sector over a selected angular range. Acoustic signals are then transmitted and echoes (or backscatter) from these acoustic signals are received. The backscatter data can be used to identify the type of a scanned tissue. As the probe is swept through the sector, many acoustic lines are processed building up a sector-shaped image of the patient. After the data is collected, an image of the blood vessel (e.g., an IVUS image) can be reconstructed using well-known techniques. This image is then visually analyzed by a cardiologist to assess the vessel components and plaque content.
A typical analysis includes determining the size of the lumen and amount of plaque in the vessel. This is performed by generating an image of the vessel (e.g., an IVUS image) and manually drawing contoured boundaries on the image where the clinician believes the luminal and the medial-adventitial borders are located. In other words, the luminal border, which demarcates the blood-intima interface, and the medial-adventitial border, which demarcates the external elastic membrane or the boundary between the media and the adventitia, are manually drawn to identify the plaque-media complex that is located there between. This is a very time consuming process. Furthermore, this process is made more difficult when multiple images are being analyzed (e.g., to recreate a 3D vascular image, etc.) or the images are of poor quality (e.g., making the boundaries more difficult to see). Thus, it would be advantageous to have a system and method of identifying a border on a vascular image that overcomes at least one of these drawbacks.